Junction boxes have long been used for making electrical connections in walls and ceilings. There have even been prior designs for placing an electrical outlet box in concrete, for example.
Conventional junction boxes, however, are typically unsuitable for carrying loads, for being cast directly in concrete, are costly to fabricate, and often have structural features which reduce the effectiveness and ease of use thereof.
For example, U.S. Pat. No. 2,983,399 to Slater et al. discloses an electrical outlet box having a seal for preventing concrete from entering the Slater box, yet the Slater outlet box is useable essentially only as a junction box, and is not designed for carrying heavy, vibrating loads, such as a ceiling fan.
U.S. Pat. No. Re. 34,603 to Caison et al. is of interest for its disclosure of an electrical junction box for support of a hanging appliance. The Caison et al. device discloses the use of square neck carriage bolts nonrotatably press fitted in the structure for carrying loads. However, loads are carried by the Caison et al. box itself, which hinders the ability of that box to carry relatively large and/or dynamic loads.
U.S. Pat. No. 1,824,708 to Davis et al. illustrates an electrical fixture and fan support which includes a bracket having a depression extending into the interior of the Davis et al. outlet box. The bracket is connected to the Davis et al. box as well as to an exterior header plate by stove bolts. Davis et al. states that a hanger bolt will be secured to the electrical fixture prior to its installation and then the worker will hoist it into position and slide the head of the hanger bolt into a head entrance and drop the hanger bolt down until it rests in a recess of the bracket. Although Davis et al. envisioned providing an extra pair of arms (Davis et al. FIG. 6) for carrying the added weight of a ceiling fan, the weight of a fixture, such a ceiling fan, will be transmitted through the single Davis et al. hanger bolt, and then through a number of screws. The reliability of the Davis et al. device is thus dependent on the individual and collective resistance to failure of a plurality of fasteners.
U.S. Pat. No. Re. 33,147 to Reiker is one of my earlier patents for a ceiling fan mounting assembly which works well and meets its intended purpose of resisting high loads and high torques. However, there is still a need for a junction box which is particularly suited for use in materials such as concrete.